S.P. Reynolds, K.J. Borkowski, C. Badenes, J.P. Hughes, U. Hwang, J.M.
Laming & J.M. Blondin
We present initial results of a 750 ks Chandra observation of the remnant of Kepler's supernova of AD 1604. We are able to separate shocked circumstellar medium, identified by O emission below 0.72 keV, and shocked ejecta, identified by Fe L and Si and S K alpha emission. The strength and prominence of iron emission, and the absence of O-rich ejecta, support the longstanding claim that Kepler resulted from a thermonuclear supernova, even though evidence for circumstellar interaction is also strong. We present images with arcsecond resolution demonstrating that the ejecta are stratified with Si and S extending beyond Fe L emission; we also find evidence for ionization of Fe decreasing inward, i.e., increasing with distance behind the reverse shock. This chemical stratification conflicts with the predictions of some Type Ia explosion models, such as sub-Chandrasekhar models or 3-D deflagrations with well-mixed ejecta. Hard continuum emission, almost certainly synchrotron, surrounds the remnant in thin filaments, as seen in other young remnants. Ejecta blobs reach to the outer blast wave in many locations. Fe K alpha emission can be seen in spectra in almost all parts of the remnant. We observe differences in Fe K alpha line centroids and profiles, due both to ionization effects and to Doppler shifts and broadening, and containing important clues to the dynamics of the remnant. We summarize the significant constraints placed on models of Type Ia supernovae, and on the progenitor of Kepler's supernova in particular, by these observations.
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